Polishing composition and rinse composition

ABSTRACT

A polishing composition for reducing the haze level of the surface of silicon wafers contains hydroxyethyl cellulose, polyethylene oxide, an alkaline compound, water, and silicon dioxide.

BACKGROUND OF THE INVENTION

The present invention relates to a polishing composition and a rinsecomposition, and more specifically to a polishing composition and arinse composition that are used in the treatment of silicon wafers toreduce the haze level of the surfaces of those silicon wafers.

Highly integrated and high-speed ULSIs are manufactured in accordance toa fine-design rule. In order to satisfy the design rule, the focal depthof recent aligners is becoming shallower, and a flawless flat surface isrequired for silicon wafers for forming semiconductor devices. Hazelevel and light point defect (LPD) are used as indices representingsurface characteristics (the degree of flaws and flatness).

Haze means milky-white clouding seen on the surface of a mirror-finishedsilicon wafer, and a haze level indicates the degree of the milky-whiteclouding. The clouding is caused by the diffused reflection of stronglight radiated onto the silicon wafer, and can be visually observed.

LPD is the defect on the surface of a silicon wafer, and is caused byforeign substances adhered on the surface (hereafter also referred to asparticles).

A polishing composition according to the first conventional methodcontains silicon dioxide, water, a water-soluble polymer (such ashydroxyethyl cellulose), a basic compound (such as ammonia), and acompound having 1 to 10 alcoholic hydroxyl groups (such as methanol).

Japanese Patent Laid-Open Publication No. 11-116942 discloses apolishing composition according to the second conventional methodcontaining silicon dioxide, water, a water-soluble polymer, and anitrogen-containing basic compound having 1 to 10 alcoholic hydroxylgroups (such as monoethanolamine).

By the action of the above-described water-soluble polymer, alcoholiccompound, or nitrogen-containing basic compound, the quantity ofparticles adhered on the wafer surface are decreased, and the LPD isimproved.

However, the polishing compositions according to the first and secondconventional methods could not satisfactorily reduce the haze level onthe surface. Therefore, there has been a demand for a treating methodand a composition that can provide silicon wafers having surfaces of areduced haze level.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a polishingcomposition, a rinse composition that can provide a silicon wafer havinga surface with a reduced haze level and a method of treating a siliconwafer using that polishing composition and that rinse composition.

One aspect of the present invention is a polishing composition used in apolishing process for reducing haze level of wafer surface. Thepolishing composition includes hydroxyethyl cellulose, polyethyleneoxide compounded in said composition in a quantity larger than 0.005% byweight and smaller than 0.5% by weight, an alkaline compound, water, andsilicon dioxide.

Another aspect of the present invention is a rinse composition used inthe process for manufacturing silicon wafer having a surface with areduced haze level. The rinse composition includes hydroxyethylcellulose, polyethylene oxide compounded in said composition in aquantity larger than 0.005% by weight and smaller than 0.5% by weight,an alkaline compound, and water.

A further aspect of the present invention is a method of polishing forproviding a silicon wafer having a surface with a reduced haze level.The method includes the steps of preparing a polishing compositioncontaining hydroxyethyl cellulose, polyethylene oxide, an alkalinecompound, water, and silicon dioxide, and contacting said polishingcomposition to the surface of said silicon wafer. Said polyethyleneoxide is compounded in said polishing composition in a quantity largerthan 0.005% by weight and smaller than 0.5% by weight.

A further aspect of the present invention is a method of rinsing forproviding a silicon wafer having a surface with a reduced haze level.The method comprising the steps of preparing a rinse compositioncontaining hydroxyethyl cellulose, polyethylene oxide, an alkalinecompound, and water, and contacting said rinse composition to thesurface of said silicon wafer after said surface has been polished. Saidpolyethylene oxide is compounded in said composition in a quantitylarger than 0.005% by weight and smaller than 0.5% by weight.

A further aspect of the present invention is a method of treating asurface of a silicon wafer for providing a silicon wafer having asurface with a reduced haze level. The method comprising the steps ofpolishing the surface of said silicon wafer using a polishingcomposition containing hydroxyethyl cellulose, polyethylene oxide, analkaline compound, water, and silicon dioxide. Said polyethylene oxideis compounded in said composition in a quantity larger than 0.005% byweight and smaller than 0.5% by weight. After polishing, a rinsecomposition is used to rinse the surface of said silicon waferimmediately after the completion of said polishing step, wherein saidrinse composition contains hydroxyethyl cellulose, polyethylene oxide,an alkaline compound, and water. The polyethylene oxide compounded insaid rinse composition is in a quantity larger than 0.005% by weight andsmaller than 0.5% by weight.

Other aspects and advantages of the present invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawing in which:

FIG. 1 is a perspective view of a polishing apparatus used in thepolishing method and the rinsing method according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present invention will be described below.

First, a method for manufacturing and treating a silicon wafer will bedescribed. In the first step, a single-crystal silicon ingot is slicedto produce a wafer. After lapping the wafer, that wafer is formed to apredetermined shape. Etching is performed for removing the deterioratedlayer caused by lapping on the surface layer of the wafer. Then theedges of the wafer are polished.

Furthermore, multistage polishing of the wafer is performed depending onthe required quality of the silicon wafer. Specifically, in order toimprove the flatness of the wafer surface, coarse polishing and finepolishing are performed. Thereafter, final polishing is performed inorder to reduce (improve) the haze level of the wafer surface. Polishingmay be performed in two stages, or may be broken up into four stages ormore.

The first embodiment relates to a polishing composition used in thepolishing process for reducing the haze level. The polishing compositioncontains the following components A to E:

-   A: hydroxyethyl cellulose (HEC)-   B: polyethylene oxide (PEO)-   C: alkaline compound-   D: water-   E: silicon dioxide

Component A, or HEC, has the function to reduce the haze level, and toimprove the wettability of the wafer surface. The average molecularweight of HEC is preferably 300,000 to 3,000,000; more preferably600,000 to 2,000,000; and most preferably 900,000 to 1,500,000. If theaverage molecular weight of HEC is lower than the above-described range,the effect of reducing the haze level is lowered. On the other hand, ifthe average molecular weight exceeds the above-described range, thepolishing composition has an excessive viscosity and is gelated, makinghandling difficult.

The content of HEC in the polishing composition is preferably 0.01 to 3%by weight, more preferably 0.05 to 2% by weight, and most preferably 0.1to 1% by weight. If the content of HEC is less than the above-describedrange, the effect of reducing the haze level is lowered. On the otherhand, if the content of HEC exceeds the above-described range, thepolishing composition has an excessive viscosity and is gelated, whichtends to make handling difficult.

Component B, or PEO, has the function to cooperate with HEC to reducethe haze level. PEO is represented by general formula (1), and n ingeneral formula (1) indicates the average degree of polymerization ofethylene oxide.HO—(CH₂CH₂O)_(n)—CH₂CH₂OH  (1)

The average molecular weight of PEO is normally 30,000 to 50,000,000;preferably 50,000 to 30,000,000; and more preferably 100,000 to10,000,000. If the average molecular weight of PEO is less than 30,000,the effect of reducing the haze level is lowered. On the other hand, ifthe average molecular weight of PEO exceeds 50,000,000, the polishingcomposition will become a gel having a high viscosity, and handling willbe difficult.

The content of PEO in the polishing composition is more than 0.005% byweight and less than 0.5% by weight, preferably more than 0.01% byweight and less than 0.4% by weight, and most preferably more than 0.03%by weight and less than 0.2%. If the content of PEO is 0.005% by weightor less, the effect of reducing the haze level is lowered. If thecontent of PEO is 0.5% by weight or more, the polishing composition willbecome a gel having a high viscosity, and handling will be difficult.

Component C, or an alkaline compound, has the function to improve thepolishing efficiency by corroding or etching the wafer surface.

As the alkaline compound, the following compounds can be used: inorganicalkaline compounds such as potassium hydroxide (PHA), sodium hydroxide(NHA), potassium hydrogen carbonate (PCAH), potassium carbonate (PCA),sodium hydrogen carbonate (NCAH), and sodium carbonate (NCA); ammoniumsalts such as ammonia (AM), tetramethyl ammonium hydroxide (TMAH),ammonium hydrogen carbonate (ACAH), and ammonium carbonate (ACA); andamines such as methylamine (MA), dimethylamine (DMA), trimethylamine(TMA), ethylamine (IA), diethylamine (DEA), triethylamine (TEA),ethylenediamine (EDA), monoethanolamine (MEA), N-(β-aminoethyl)ethanolamine (AEEA), hexamethylenediamine (HMDA), diethylenetriamine(DETA), triethylenetetramine (TETA), piperazine anhydride (PIZ),piperazine hexahydride, 1-(2-aminoethyl) piperazine (AEPIZ), andN-methylpiperazine (MPIZ). The alkaline compound can be used alone or incombination of two or more. The abbreviations indicated in parentheseswill be used in the following description.

The preferred alkaline compounds are PHA, NHA, PCAH, PCA, NCAH, NCA, AM,TMAH, ACAH, ACA, PIZ, piperazine hexahydride, AEPIZ, and MPIZ, whichhave relatively low amine odor. PHA, NHA, AM, TMAH, PIZ, and piperazinehexahydride are preferred also because these compounds do not interferewith the function of the components of HEC and PEO.

The preferred content of Component C in the polishing composition is asfollows:

When Component C is PHA, NHA, PCAH, PCA, NCAH, NCA, AM, TMAH, ACAH, ACA,MA, DMA, TMA, EA, DEA, TEA, EDA, MEA, AEEA, HMDA, DETA, or TETA, thecontent of Component C is preferably 0.02 to 4% by weight, morepreferably 0.03 to 3% by weight, and most preferably 0.2 to 2% byweight.

When Component C is PIZ, AEPIZ, or MPIZ, the content of Component C ispreferably 0.005 to 3% by weight, more preferably 0.01 to 2% by weight,and most preferably 0.1 to 0.5% by weight.

When Component C is piperazine hexahydride, the content is preferably0.01 to 6% by weight, more preferably 0.02 to 3% by weight, and mostpreferably 0.2 to 1% by weight.

If the content of Component C is lower than the preferred range, thepolishing acceleration function by Component C is weakened, andpolishing speed is lowered. On the other hand, if the content ofComponent C exceeds the preferred range, the polishing composition isgelated, and since further polishing acceleration function cannot beobtained, the content of Component C exceeding the preferred range isuneconomical. Furthermore, since the etching power increasesexcessively, the wafer surface is roughened.

Component D, or water, has the function to disperse silicon dioxide, andto dissolve HEC, PEO, and the alkaline compound. In order not tointerfere with the functions of other Components A, B, C, and E, thewater of a lowered impurity content is preferred, such as ion-exchangedwater, pure water, ultra-pure water, and distilled water.

Component E, or silicon dioxide, has the function to mechanically polishthe wafer surface. As the silicon dioxide, for example, colloidal silica(colloidal SiO₂) and fumed silica (fumed SiO₂) can be used. Of these,colloidal silica is preferred because it can polish the wafer surfacewith a high degree of precision.

The preferred particle diameters of Component E will be described. Twotypes of particle diameters are the average particle diameter D_(SA)obtained on the basis of the specific surface area measured inaccordance with the method for measuring the specific surface area ofpowder by a gas suction (SET method), and the average particle diameterD_(N4) calculated from laser scattering.

When Component E is colloidal silica, the average particle diameterD_(SA) is preferably 5 to 300 nm, more preferably 5 to 200 nm, and mostpreferably 5 to 120 nm; and the average particle diameter D_(N4) ispreferably 5 to 300 nm, more preferably 10 to 200 nm, and mostpreferably 15 to 150 nm. If the average particle diameter of colloidalsilica is smaller than the above-described range, sufficient polishingspeed cannot be achieved. On the other hand, if the average particlediameter of colloidal silica exceeds the above-described range, thesurface roughness of the silicon wafer tends to increase, and defects ofthe wafer surface such as scratches are easily produced to deterioratethe haze level.

When Component E is fumed silica, the average particle diameter D_(SA)is preferably 10 to 300 nm, more preferably 10 to 200 nm, and mostpreferably 10 to 150 nm; and the average particle diameter D_(N4) ispreferably 30 to 500 nm, more preferably 40 to 400 nm, and mostpreferably 50 to 300 nm. If the average particle diameter of fumedsilica is smaller than the above-described range, sufficient polishingspeed cannot be achieved. On the other hand, if the average particlediameter of fumed silica exceeds the above-described range, the surfaceroughness of the silicon wafer tends to increase, and defects of thewafer surface such as scratches are easily produced to deteriorate thehaze level.

Silicon dioxide may contain metallic impurities. The metallic impuritiesinclude transition metals, such as iron (Fe), nickel (Ni), and copper(Cu); calcium (Ca), magnesium (Mg), or the hydroxides and oxidesthereof. The total content of the metallic impurities in silicondioxide, as measured in a 20 wt-% aqueous solution of silicon dioxide ispreferably 300 ppm or less, more preferably 100 ppm or less, and mostpreferably 0.3 ppm or less. If the content of metallic impuritiesexceeds 300 ppm, silicon wafers are easily contaminated by the metallicimpurities.

The contamination of silicon wafers by metallic impurities means theadhesion of metallic impurities having a large diffusion coefficientsuch as copper, and the diffusion of the metallic impurities into thesilicon wafers due to polishing. If a device is formed using ametal-contaminated silicon wafer, the metallic impurities diffused onthe surface of or in the wafer may cause the defect of thesemiconductor, such as short-circuiting and leakage.

The content of silicon dioxide in the polishing composition ispreferably 0.1 to 40% by weight, more preferably 1 to 30% by weight, andmost preferably 3 to 20% by weight. It the content of silicon dioxide isless than 0.1% by weight, sufficient polishing speed cannot be achieved.On the other hand, if the content of silicon dioxide exceeds 40% byweight, the viscosity of the polishing composition will excessivelyincrease, the polishing composition will be gelated, and handling willbecome difficult.

The polishing composition may contain various additive components, suchas chelating agents, surfactants, and preservatives. The content of theadditive components is determined in accordance with the common practiceof polishing compositions.

The pH of the polishing composition is preferably 9 to 12, and mostpreferably 10 to 11. If the pH of the polishing composition is lowerthan 9, the content of Component C is low, and sufficient polishingspeed cannot be achieved. On the other hand, if the pH of the polishingcomposition exceeds 12, the polishing composition may be gelated.

The polishing composition is prepared by adding Components A, B, C, andE to water, and stirring them using a blade-type stirrer, or dispersingusing an ultrasonic dispersing apparatus The order to add Components A,B, C, and E to water is not limited.

In the first embodiment, the polishing composition having a relativelyhigh concentration is prepared in order to facilitate the storage andtransportation of the polishing composition. The polishing compositionis practically used in polishing processes after diluting. For diluting,the above-described impurity-reduced water is used. When a previouslydiluted polishing composition is prepared, the dilution ratio of thepolishing composition is preferably 50 or less, more preferably 40 orless, and most preferably 20 or less. If the dilution ratio exceeds 50,the volume and weight of the diluted solution increase, and thetransportation costs tend to be expensive.

Next, the apparatus 11 for polishing silicon wafers will be describedreferring to FIG. 1.

The polishing apparatus 11 has a disc-type turntable 12 whereon apolishing pad 14 is bonded. The turntable 12 rotates around a firstrotation shaft 13 installed on the lower center thereof. One or aplurality of disc-type wafer holders 15 (only one is shown in FIG. 1)are installed above the turntable 12, each wafer holder 15 is rotated bya second rotation shaft 16 fixed to the upper center thereof, and adisc-type ceramic plate 17 is fixed to the bottom surface.

To the bottom surface of the ceramic plate 17, a polyurethane sheet (notshown), and a disc-type wafer holding plate 19 having four wafer-holdingholes 18 is detachably fixed. The polishing composition 20 is fed to thepolishing pad 14 from the nozzle 21 a of the feeder 21 installed abovethe turntable 12. When multistage polishing is performed, a plurality ofrespectively optimized polishing compositions are prepared for aplurality of polishing processes, and these polishing compositions areseparately fed to the polishing pad 14 from a plurality of feeders 21.

Next, a method will be described for polishing a silicon wafer using thepolishing composition.

When the wafer surface is polished in, for example, three stages, thesilicon wafer is first held in the wafer holder 15 by, for example,suction while being accommodated in a wafer-holding hole 18 with thesurface to be polished facing downward. While rotating the wafer holder15 and the turntable 12, the polishing composition for first polishingis fed to the polishing pad 14 from the feeder 21. The wafer holder 15is moved downward to push a silicon wafer against the polishing pad 14.Thus, the first polishing is performed on the wafer surface.

After the first polishing, second polishing is performed. The waferholder 15 is once separated from the turntable 12. While feeding thecomposition for second polishing onto the polishing pad 14 from thefeeder for the second polishing, the wafer holder 15 is moved downwardto push a silicon wafer against the polishing pad 14. Thus, the secondpolishing is performed on the wafer surface.

After the second polishing, third polishing for lowering the haze levelof the wafer surface is performed by using the polishing composition 20according to the present invention. First, the wafer holder 15 is onceseparated from the turntable 12. While feeding the composition 20 forthird polishing onto the polishing pad 14 from the feeder 21 for thethird polishing, the wafer holder 15 is moved downward to push a siliconwafer against the polishing pad 14. Thus, the third polishing isperformed on the wafer surface.

Although the case wherein one side of a silicon wafer is polished isdescribed in the above description, the present invention can be appliedto the case wherein both sides are simultaneously polished using adouble-side polishing machine.

According to the first embodiment, the following advantage can beobtained.

The polishing composition of the first embodiment contains HEC and PEO.By the synergic action of HEC and PEO, the surface roughness of wafersis efficiently reduced, and the haze level is reduced in comparison withconventional polishing compositions. The adhesion of particles, such asthe components of the polishing composition and chips generated bypolishing (abrasive shavings) onto the wafer surface is also inhibited,and the deterioration of LPD is prevented.

Since the polishing composition contains an alkaline compound (ComponentC), the polishing speed is improved.

Next, the second embodiment of the present invention will be described.The second embodiment related to a rinse composition used in the rinsingprocess performed after the polishing process for reducing the hazelevel of the wafer surface The rinse composition contains the followingcomponents A to D:

-   A: HEC,-   B: PEO,-   C: alkaline compound, and-   D: water.

The details of each component are as described for the above polishingcomposition.

Component C, or an alkaline compound, is used in order to adjust the pHof the rinse composition, and to reduce the haze level of the wafersurface. If a rapid change in pH occurs on the surface of a polishedwafer, surface roughness is easily produced. Therefore, it is preferredthat the pH of the rinse composition is almost the same level as the pHof the polishing composition. If the pH of the rinse composition isconsiderably lower than the pH of the polishing composition, thepolishing composition remaining on the surface of the polishing padreacts with the rinse composition on the wafer surface to form a gel.Since the removal of the gel from the wafer surface is difficult, andthe gel causes the plugging of the polishing pad, the formation of thegel is not preferred. On the other hand, if the pH of the rinsecomposition is considerably higher than the pH of the polishingcomposition, the wafer surface is easily roughened.

The rinse composition is prepared by adding Components A, B, and C towater, and stirring using a blade-type stirrer or dispersing using anultrasonic dispersing apparatus. The order to add Components A, B, and Cto water is not limited.

The polishing composition having a relatively high concentration isprepared in order to facilitate the storage and transportation of therinse composition. The rinse composition is practically used in rinseprocesses after diluting. For diluting, the above-describedimpurity-reduced water is used. When a previously diluted rinsecomposition is manufactured, the dilution ratio of the rinse compositionis preferably 100 or less, more preferably 80 or less, and mostpreferably 40 or less. If the dilution ratio exceeds 100, the volume andweight of the diluted solution increase, and the transportation coststend to be expensive.

Next, a method for rinsing a silicon wafer using the above-describedrinse composition will be described.

Immediately after the completion of polishing for reducing the hazelevel, the feeder 21 is replaced with a feeder for the rinse compositionwhile maintaining the state wherein the wafer holder 15 is contacted tothe turntable 12. The operating conditions of the polishing apparatusare switched to rinse conditions. The polishing composition remains onthe water surface and the polishing pad 14. The polishing pad 14 is usedas a pad for rinsing. The rinse composition is fed onto the polishingpad 14 from the feeder for the rinse composition. The wafer surface isrinsed by pushing the silicon wafer against the polishing pad 14.

Although the case wherein one side of a silicon wafer is rinsed isdescribed in the above description, the present invention can be appliedto the case wherein both sides are simultaneously rinsed using adouble-side polishing machine.

According to the second embodiment, the following advantage can beobtained.

The rinse composition of the second embodiment contains HEC and PEO. Inthe rinsing method of the second embodiment, after the completion ofpolishing for reducing the haze level, the wafer surface whereon thepolishing composition remains is rinsed using the rinse composition.Therefore a mixture of the polishing composition remaining on the wafersurface, the surface on and in the polishing pad, and the rinsecomposition is formed. Since the mixture contains a trace of silicondioxide (Component E) derived from the polishing composition, the wafersurface is polished to some extent by silicon dioxide in the rinsingprocess. By the synergic action of HEC and PEO, the surface roughness ofwafers is reduced, and the haze level is reduced in comparison withconventional rinse compositions. Since the adhesion of particles is alsoreduced, the LPD is improved.

According to the rinsing process of the second embodiment, the polishingand rinsing of the wafer surface are sequentially performed. Therefore,the labor for once removing the silicon wafer after polishing the wafersurface from the wafer holding hole 18, and for mounting the siliconwafer to the rinsing apparatus can be eliminated, and the occurrence ofetching or contamination of the wafer surface caused by the polishingcomposition can be prevented. The drying up of the wafer surface afterpolishing is also prevented, and the adhesion of silicon dioxide in thepolishing composition on the wafer surface can be prevented. As aresult, the LPD is improved. Since polishing and rinsing can beperformed using the same apparatus, the time for treating the wafersurface can be reduced, and the costs for the polishing and rinsingprocesses can be reduced.

The embodiments may be altered as follows:

After the completion of polishing or rinsing, the wafer surface may bescrub-cleaned using pure water. Scrub cleaning is a method for scrubbingthe wafer surface using impurity-reduced water, such as pure water andultra-pure water, with a sponge made of polyvinyl alcohol or the like.

The polishing composition and the rinse composition may contain hydrogenperoxide. The oxide film formed by hydrogen peroxide on the wafersurface prevents the adhesion of particles directly on the wafersurface, and improves the LPD.

The rinse composition may contain a trace of silicon dioxide (ComponentE). In this case, even if the polishing composition does not remain onthe wafer surface or the surface of or in the polishing pad, the hazelevel is reduced by the rinsing treatment of the wafer surface.

Next, the examples and comparative examples of the present inventionwill be described.

EXAMPLES 1 TO 26 AND COMPARATIVE EXAMPLES 1 TO 19

Polishing Composition

The polishing composition of Example 1 was prepared by mixing HEC(Component A), PEO (Component B), a 29 wt-% aqueous solution of ammonia(Component C), ultra-pure water (Component D), and colloidal silica(Component E). The contents of HEC, PEO, and AM in the polishingcomposition are shown in Table 1. The quantity of AM in the followingdescription and tables is the quantity of a 29 wt-% aqueous solution ofammonia, and the quantity of TMAH is the quantity of a 25 wt-% aqueoussolution of TMAH.

HEC and PEO are components to reduce the haze level, and ammonia is acomponent to accelerate polishing. The content of colloidal silica inthe polishing composition was 10% by weight. The total content of iron,nickel, copper, and calcium in the 20 wt-% aqueous solution of colloidalsilica was 20 ppb or less.

The average particle diameter D_(SA) of colloidal silica measured usinga FlowSorb II2300, the trade name of Micromeritics GmbH, was 35 nm. Theaverage particle diameter D_(N4) of colloidal silica measured using anN4 Plus Submicron Particle Sizer, the trade name of Beckman Coulter,Inc. was 70 nm.

In Examples 2 to 26 and Comparative Examples 1 to 19, polishingcompositions were prepared in the same manner as in Example 1 exceptthat the kinds and contents of the components to reduce the haze leveland the components to accelerate polishing were changed as shown inTables 1 and 2.

Each polishing composition of Examples 1 to 26 and Comparative Examples1 to 19 was diluted 20 times (volume ratio) with ultra-pure water, andthe surface of a silicon wafer was polished using the diluted polishingcomposition under the following conditions.

-   Polishing apparatus: Single-side polishing apparatus (SPM-15:    Fujikoshi Machinery Corp. with 4 wafer holders)-   Articles to be polished: Four 6-inch silicon wafers/wafer holder-   Load: 9.4 kPa-   Turntable rotating speed: 30 rpm-   Wafer holder rotating speed: 30 rpm-   Polishing pad: Surfin 000 (suede type, manufactured by Fujimi    Incorporated)-   Feed speed of the composition; 500 ml/min-   Polishing time: 8 min-   Temperature of the composition: 20° C.

As silicon wafers for testing Examples 1 to 24 and Comparative Examples1 to 17, 6-inch silicon wafers (p-type, crystal orientation <100>,resistivity: less than 0.01 Ω·cm) from which the surface layers had beenpreviously removed by 10 μm by polishing using a polishing composition(GLANZOX-1101, manufactured by Fujimi Incorporated) were used.

As silicon wafers for testing Example 25 and Comparative Example 18,6-inch silicon wafers (p-type, crystal orientation <100>, resistivity:0.01 Ω·cm or more and less than 0.1 Ω·cm) from which the surface layershad been previously removed by 10 μm by polishing using a polishingcomposition (GLANZOX-1101, manufactured by Fujimi Incorporated) wereused.

As silicon wafers for testing Example 26 and Comparative Example 19,6-inch silicon wafers (p-type, crystal orientation <100>, resistivity:0.1 Ω·cm or more) from which the surface layers had been previouslyremoved by 10 μm by polishing using a polishing composition(GLANZOX-1101, manufactured by Fujimi Incorporated) were used.

The silicon wafers after polishing were subjected to scrub cleaning for10 seconds using pure water, and SC-1 cleaning In SC-1 cleaning, asolution of ammonia (29 wt-% solution):hydrogen peroxide (31%solution):pure water=1:1:10 (volume ratio) was used.

The haze level (hereafter abbreviated as HL) and LPD of the siliconwafers after cleaning were evaluated. For Examples 2, 3, 5, and 10 to14, and Comparative Examples 5, 10 to 13, and 16, the surface conditionswere also evaluated. The results of evaluation are shown in Tables 1 and2.

The abbreviations in the tables are as follows:

Ethanol: EtOH

Guar gum: GGG

Polyacrylic amide: PAAM

Potassium chloride: CP

Disophylane: SPH

Polyvinyl alcohol (average degree of polymerization: 1,400; degree ofsaponification: 95%): PVA

Polyethylene glycol: PEG

(1) Haze level

The haze levels of silicon wafers after cleaning were measured using anAMS-AWIS 3110 (trade name of ADE Company). The measured haze levels wereevaluated by five scales of less than 0.05 ppm (⋆). 0.05 ppm or more andless than 0.075 ppm (⊚), 0.075 ppm or more and less than 0.1 ppm (◯),0.1 ppm or more and less than 0.2 ppm (Δ), and 0.2 ppm or more (X).

(2) LPD

The number of particles of a size of 0.1 μm or larger in silicon wafersafter cleaning was counted using an AMS-AWIS 3110. The LPD was evaluatedby three scales of less than 50 (◯), 50 or more and less than 300 (Δ),and 300 or more (X).

(3) Surface Conditions

The surface conditions of silicon wafers after cleaning were observedusing an atomic force microscope (D 3000 manufactured by DigitalInstruments). The observed range was a square area of a side of 10 μm,and ten areas were observed. The surface conditions were evaluated byfour scales of very good without scratches (⊚), good with few scratches(◯), poor with scratches (Δ), and very poor with many scratches (X).

In the polishing compositions of Examples 1 to 26 that contain both HECand PEO, the evaluations of the haze level and LPD were fine. In thepolishing compositions of Examples 2, 3, 5, and 10 to 14 that containedboth HEC and PEO, the evaluations of the surface conditions were high,and it was seen that the formation of scratches was inhibited.

On the other hand, the evaluations of haze levels were poor in thepolishing compositions of Comparative Examples 2 to 4, 6 to 8, and 15that contained neither HEC nor PEO, the polishing composition ofComparative Examples 1, 5, 9–12, 16 and 17 that contained either one ofHEC and PEO, the polishing composition of Comparative Example 13 of thePEO content of 0.005% by weight or less, and the polishing compositionof Comparative Example 14 of the PEO content of 0.5% by weight or moreIn Comparative Examples 5, 10 to 13, and 16, the evaluations of surfaceconditions were also poor. The haze levels of polishing compositions ofComparative Examples 18 and 19 that contained either one of HEC and PEOwere poorer than the haze levels of Examples 25 and 26.

It was known from the above results, that the polishing compositions ofExamples 1 to 26 that contained both HEC and PEO were superior to thepolishing compositions of Comparative Examples 1 to 19 that lacked atleast one of HEC and PEO.

EXAMPLES 27 TO 52 AND COMPARATIVE EXAMPLES 20 TO 36

Rinse Composition

Rinse compositions of Example 27 was prepared by mixing HEC (ComponentA), PEO (Component B), AM (Component C), and ultra-pure water (ComponentD). HEC and PEO are the component to reduce the haze level, andComponent C is a component to adjust pH The contents of HEC, PEO, and AMin the rinse composition are shown in Table 3.

The compositions of the rinse compositions of Examples 28 to 52 andComparative Examples 20 to 36 are shown in Tables 3 and 4. Each rinsecomposition of Examples 27 to 52 and Comparative Examples 20 to 36 wasdiluted 20 times with ultra-pure water.

At the same time of the completion of polishing using the polishingcomposition of Example 5 under the above-described polishing conditions,the operating conditions of the polishing apparatus were switched to thefollowing rinsing conditions, and rinsing was performed using thediluted rinse composition.

<Rinsing Conditions>

-   Load: 2 kPa-   Wafer holder rotation speed: 62 rpm-   Feeding speed of the composition: 2,000 ml/min-   Rinsing time: 30 seconds    Other conditions were the same as in the polishing conditions    described above.

As silicon wafers for testing the rinse compositions of Examples 27 to50 and Comparative Examples 20 to 34, 6-inch silicon wafers (p-type,crystal orientation <100>, resistivity: less than 0.01 Ω·cm) from whichthe surface layers had been previously removed by 10 μm by polishingusing a polishing composition (GLANZOX-1101, manufactured by FujimiIncorporated) were used.

The rinsing tests for the rinse compositions of Example 51 andComparative Example 35 were different from the tests for the rinsecompositions of Examples 27 to 50 and Comparative Examples 20 to 34 onlyin the following aspects. Specifically the silicon wafers for the testswere 6-inch silicon wafers (p-type, crystal orientation <100>,resistivity: 0.01 Ω·cm or more and less than 0.1 Ω·cm) from which thesurface layers had been previously removed by 10 μm by polishing using apolishing composition (GLANZOX-1101, manufactured by FujimiIncorporated), and polished using the polishing composition ofComparative Example 19 before rinsing.

The rinsing tests for the rinse compositions of Example 52 andComparative Example 36 were different from the tests for the rinsecompositions of Examples 27 to 50 and Comparative Examples 20 to 34 onlyin the following aspects. Specifically the silicon wafers for the testswere 6-inch silicon wafers (p-type, crystal orientation <100>,resistivity: 0.1 Ω·cm or more) from which the surface layers had beenpreviously removed by 10 μm by polishing using a polishing composition(GLANZOX-1101, manufactured by Fujimi Incorporated).

After rinsing using each rinse composition, scrub cleaning using purewater for 10 seconds, and SC-1 cleaning were performed. The siliconwafers after treatment were evaluated. The results of evaluation areshown in Tables 3 and 4.

The evaluations of the haze level and LPD were high in the rinsecompositions of Examples 27 to 52 that contained both HEC and PEO.

On the other hand, the evaluations of the haze level were low in therinse compositions of Comparative Examples 20, 21, 25 to 28, and 32 to34 that contained either one of HEC or PEO; the rinse compositions ofComparative Examples 22 to 24 and 31 that contained neither HEC nor PEO;the rinse composition of Comparative Example 29 that contained 0.005% byweight or less PEO; the rinse composition of Comparative Example 30 thatcontained 0.5% by weight or more PEO; and Comparative Examples 35 and 36that contained either one of HEC or PEO.

The present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

TABLE 1 for reducing haze level MW MW MW Examples (×10³) wt % (×10³) wt% (×10³) wt % wt %  1 HEC 1200 0.1 PEO 150~400 0.1 — —  2 HEC 1200 0.25PEO 150~400 0.01 — —  3 HEC 1200 0.25 PEO 150~400 0.1 — —  4 HEC 12000.25 PEO 150~400 0.1 EtOH — 2.0 —  5 HEC 1200 0.25 PEO 150~400 0.3 — — 6 HEC 1200 0.5 PEO 150~400 0.1 — —  7 HEC 1000 0.25 PEO 150~400 0.1 — — 8 HEC 1600 0.25 PEO 150~400 0.1 — —  9 HEC 1200 0.25 PEO  80~120 0.1 —— 10 HEC 1200 0.25 PEO 1700~2200 0.1 — — 11 HEC 1200 0.25 PEO 6000~80000.1 — — 12 HEC 1200 0.25 PEO 150~400 0.1 PVA — 0.25 — 13 HEC 1200 0.25PEO 150~400 0.1 PEG 0.6 0.1 — 14 HEC 1200 0.25 PEO 150~400 0.1 PEG 0.60.1 PVA 0.25 15 HEC 1200 0.25 PEO 150~400 0.1 — — 16 HEC 1200 0.25 PEO150~400 0.1 — — 17 HEC 1200 0.25 PEO 150~400 0.1 — — 18 HEC 1200 0.25PEO 150~400 0.1 — — 19 HEC 1200 0.25 PEO 150~400 0.1 — — 20 HEC 12000.25 PEO 150~400 0.1 — — 21 HEC 1200 0.25 PEO 150~400 0.1 — — 22 HEC1200 0.25 PEO 150~400 0.1 — — 23 HEC 1200 0.25 PEO 150~400 0.1 — — 24HEC 1200 0.25 PEO 150~400 0.1 — — 25 HEC 1200 0.25 PEO 150~400 0.1 — —26 HEC 1200 0.25 PEO 150~400 0.1 — — for enhancing polishing rate hazesurface Examples wt % wt % wt % wt % level LPD condition  1 AM 1.0 — — —⊚ Δ —  2 AM 1.0 — — — ⊚ Δ ∘  3 AM 1.0 — — — ⋆ Δ ⊚  4 AM 1.0 — — — ⋆ ∘ — 5 AM 1.0 — — — ⊚ Δ ⊚  6 AM 1.0 — — — ⊚ Δ —  7 AM 1.0 — — — ⋆ Δ —  8 AM1.0 — — — ⋆ Δ —  9 AM 1.0 — — — ⋆ Δ — 10 AM 1.0 — — — ⋆ Δ ⊚ 11 AM 1.0 —— — ⋆ Δ ⊚ 12 AM 1.0 — — — ⊚ Δ ⊚ 13 AM 1.0 — — — ⋆ Δ ⊚ 14 AM 1.0 — — — ⊚Δ ⊚ 15 PHA 0.3 — — — ⋆ Δ — 16 TMAH 0.5 — — — ⋆ Δ — 17 PIZ 0.3 — — — ⋆ Δ— 18 AM 0.5 PHA 0.15 — — ⋆ Δ — 19 AM 0.5 TMAH 0.25 — — ⋆ Δ — 20 AM 0.5PIZ 0.15 — — ⋆ Δ — 21 AM 0.4 PHA 0.1 TMAH 0.2 — ⋆ Δ — 22 AM 0.4 PHA 0.1PIZ 0.1 — ⋆ Δ — 23 AM 0.4 TMAH 0.2 PIZ 0.1 — ⋆ Δ — 24 AM 0.25 PHA 0.1TMAH 0.1 PIZ 0.1 ⋆ Δ — 25 AM 1.0 — — — ⋆ Δ — 26 AM 1.0 — — — ⋆ Δ — *AM:29 wt % ammonium solution

TABLE 2 for reducing haze level for enhancing Comparative MW MW MWpolishing rate haze surface examples (×10³) wt % (×10³) wt % (×10³) wt %wt % level LPD condition 1 HEC 1200 0.25 EtOH — 2.0 — AM 1.0 ∘ ∘ — 2 GGG— 0.03 — — CP 0.2 x x — 3 PAAM — 0.03 — — CP 0.2 x x — 4 SPH — 0.03 — —CP 0.2 x x — 5 HEC 1200 0.25 — — AM 1.0 ∘ Δ x 6 PVA — 0.25 — — AM 1.0 ∘Δ — 7 PEG 0.6 0.1 — — AM 1.0 Δ x — 8 PEG 20 0.1 — — AM 1.0 Δ x — 9 PEO150~400 0.1 — — AM 1.0 ∘ x — 10 HEC 1200 0.25 PVA — 0.25 — AM 1.0 ∘ Δ x11 HEC 1200 0.25 PEG 0.6 0.1 — AM 1.0 ∘ Δ x 12 HEC 1200 0.25 PEG 20 0.1— AM 1.0 ∘ x x 13 HEC 1200 0.25 PEO 150~400 0.003 — AM 1.0 ∘ Δ Δ 14 HEC1200 0.25 PEO 150~400 0.5 — AM 1.0 ∘ Δ — 15 PVA — 0.25 PEG 0.6 0.1 — AM1.0 ∘ x — 16 PEG 0.6 0.1 PEO 150~400 0.1 — AM 1.0 Δ x x 17 HEC 1200 0.25PVA — 0.25 PEG 0.6 0.1 AM 1.0 ∘ x — 18 HEC 1200 0.25 — — AM 1.0 ∘ Δ — 19HEC 1200 0.25 — — AM 1.0 ⊚ Δ — *AM: 29 wt % ammonium solution

TABLE 3 for reducing haze level MW MW MW Examples (×10³) wt % (×10³) wt% (×10³) wt % wt % 27 HEC 1200 0.1 PEO 150~400 0.1 — — 28 HEC 1200 0.25PEO 150~400 0.01 — — 29 HEC 1200 0.25 PEO 150~400 0.1 — — 30 HEC 12000.25 PEO 150~400 0.1 EtOH — 2.0 — 31 HEC 1200 0.25 PEO 150~400 0.3 — —32 HEC 1200 0.5 PEO 150~400 0.1 — — 33 HEC 1000 0.25 PEO 150~400 0.1 — —34 HEC 1600 0.25 PEO 150~400 0.1 — — 35 HEC 1200 0.25 PEO  80~120 0.1 —— 36 HEC 1200 0.25 PEO 1700~2200 0.1 — — 37 HEC 1200 0.25 PEO 6000~80000.1 — — 38 HEC 1200 0.25 PEO 150~400 0.1 PVA — 0.25 — 39 HEC 1200 0.25PEO 150~400 0.1 PEG 0.6 0.1 — 40 HEC 1200 0.25 PEO 150~400 0.1 PEG 0.60.1 PVA 0.25 41 HEC 1200 0.25 PEO 150~400 0.1 — — 42 HEC 1200 0.25 PEO150~400 0.1 — — 43 HEC 1200 0.25 PEO 150~400 0.1 — — 44 HEC 1200 0.25PEO 150~400 0.1 — — 45 HEC 1200 0.25 PEO 150~400 0.1 — — 46 HEC 12000.25 PEO 150~400 0.1 — — 47 HEC 1200 0.25 PEO 150~400 0.1 — — 48 HEC1200 0.25 PEO 150~400 0.1 — — 49 HEC 1200 0.25 PEO 150~400 0.1 — — 50HEC 1200 0.25 PEO 150~400 0.1 — — 51 HEC 1200 0.25 PEO 150~400 0.1 — —52 HEC 1200 0.25 PEO 150~400 0.1 — — for pH adjustment haze Examples wt% wt % wt % wt % level LPD 27 AM 1.0 — — — ⊚ ∘ 28 AM 1.0 — — — ⊚ ∘ 29 AM1.0 — — — ⊚ ∘ 30 AM 1.0 — — — ⊚ ∘ 31 AM 1.0 — — — ⊚ ∘ 32 AM 1.0 — — — ⊚∘ 33 AM 1.0 — — — ⊚ ∘ 34 AM 1.0 — — — ⊚ ∘ 35 AM 1.0 — — — ⊚ ∘ 36 AM 1.0— — — ⊚ ∘ 37 AM 1.0 — — — ⊚ ∘ 38 AM 1.0 — — — ⊚ ∘ 39 AM 1.0 — — — ⊚ ∘ 40AM 1.0 — — — ⊚ ∘ 41 PHA 0.3 — — — ⊚ ∘ 42 TMAH 0.5 — — — ⊚ ∘ 43 PIZ 0.3 —— — ⊚ ∘ 44 AM 0.5 PHA 0.15 — — ⊚ ∘ 45 AM 0.5 TMAH 0.25 — — ⊚ ∘ 46 AM 0.5PIZ 0.15 — — ⊚ ∘ 47 AM 0.4 PHA 0.1 TMAH 0.2 — ⊚ ∘ 48 AM 0.4 PHA 0.1 PIZ0.1 — ⊚ ∘ 49 AM 0.4 TMAH 0.2 PIZ 0.1 — ⊚ ∘ 50 AM 0.25 PHA 0.1 TMAH 0.1PIZ 0.1 ⊚ ∘ 51 AM 1.0 — — — ⊚ ∘ 52 AM 1.0 — — — ⋆ ∘ *AM: 29 wt %ammonium solution

TABLE 4 for reducing haze level Comparative MW MW MW for pH adjustmenthaze examples (×10³) wt % (×10³) wt % (×10³) wt % wt % level LPD 20 HEC1200 0.25 EtOH — 2.0 — AM 1.0 ∘ ∘ 21 HEC 1200 0.25 — — AM 1.0 ∘ Δ 22 PVA— 0.25 — — AM 1.0 Δ Δ 23 PEG 0.6 0.1 — — AM 1.0 Δ Δ 24 PEG 20 0.1 — — AM1.0 Δ Δ 25 PEO 150~400 0.1 — — AM 1.0 Δ Δ 26 HEC 1200 0.25 PVA — 0.25 —AM 1.0 Δ Δ 27 HEC 1200 0.25 PEG 0.6 0.1 — AM 1.0 Δ Δ 28 HEC 1200 0.25PEG 20 0.1 — AM 1.0 Δ Δ 29 HEC 1200 0.25 PEO 150~400 0.003 — AM 1.0 ∘ Δ30 HEC 1200 0.25 PEO 150~400 0.5 — AM 1.0 ∘ Δ 31 PVA — 0.25 PEG 0.6 0.1— AM 1.0 ∘ Δ 32 PVA — 0.25 PEO 150~400 0.1 — AM 1.0 Δ Δ 33 PEG 0.6 0.1PEO 150~400 0.1 — AM 1.0 Δ Δ 34 HEC 1200 0.25 PVA — 0.25 PEG 0.6 0.1 AM1.0 Δ Δ 35 HEC 1200 0.25 — — AM 1.0 ∘ Δ 36 HEC 1200 0.25 — — AM 1.0 ⊚ Δ*AM: 29 wt % ammonium solution

1. A polishing composition used in a polishing process for reducing hazelevel of wafer surface, comprising: hydroxyethyl cellulose compounded insaid composition in a quantity of 0.05 to 2% by weight and having anaverage molecular weight in the range of 300,000 to 2,000,000;polyethylene oxide compounded in said composition in a quantity largerthan 0.005% by weight and smaller than 0.5% by weight and having anaverage molecular weight in the range of 50,000 to 10,000,000; ammoniacompounded in said composition in a quantity 0.02 to 4% by weight;water; and silicon dioxide.
 2. The polishing composition according toclaim 1, wherein the total content of iron, nickel, copper, and calciumin the silicon dioxide, as measured in a 20 wt-% aqueous solution ofsaid silicon dioxide, is 300 ppm or less.
 3. The polishing compositionaccording to claim 1, wherein the content of hydroxyethyl cellulose inthe polishing composition is 0.1 to 1% by weight.
 4. The polishingcomposition according to claim 1, wherein the content of silicon dioxidein the polishing composition is 3 to 20% by weight.
 5. The polishingcomposition according to claim 1, wherein the average molecular weightof hydroxyethyl cellulose in the polishing composition is 600,000 to2,000,000.
 6. The polishing composition according to claim 1, whereinthe average molecular weight of hydroxyethyl cellulose in the polishingcomposition is 900,000 to 1,500,000.
 7. The polishing compositionaccording to claim 1, wherein the content of polyethylene oxide in thepolishing composition is lager than 0.01% by weight and smaller than0.4% by weight.
 8. The polishing composition according to claim 1,wherein the content of polyethylene oxide in the polishing compositionis larger than 0.03% by weight and smaller than 0.2% by weight.
 9. Thepolishing composition according to claim 1, wherein the averagemolecular weight of polyethylene oxide in the polishing composition is100,000 to 10,000,000.
 10. The polishing composition according to claim1, wherein the content of ammonia in the polishing composition is 0.03to 3% by weight.
 11. The polishing composition according to claim 1,wherein the content of ammonia in the polishing composition is 0.2 to 2%by weight.